Due to the speed of a traveling archery arrow, its ballistics are strongly affected by gravity. It follows that the parabolic path followed by an arrow is largely dependent upon the distance to a target. This is taken into account when calibrating the vertical position of a bow sight to a particular target distance.
Adjustable bow sights which allow a sight element to be vertically adjusted to accommodate a range of target distances are well known in the art. For example, my U.S. Pat. No. 4,541,179 describes a bow sight wherein a sight carrier plate is adjustably attached to a support by both a lever and a linking piece. The lever can be pivoted about a hollow rivet which connects the lever to the support. Adjusting the lever causes the carrier plate to travel vertically, thereby altering the elevation of a sighting element on the carrier plate as desired. While my sight has been highly successful, there is a further need for a bow sight having a means for even quicker and more precise fine tuning and recalibration.
U.S. Pat. No. 5,092,052 describes another adjustable bow sight having a base plate, a vertically adjustable sight mounting plate engaging linear tracks and a retaining plate. This sight also fails to meet the above identified needs.
Adjustable sights such as in my U.S. Pat. No. 4,541,179 can be calibrated experimentally by firing arrows at a target from several measured distances. Further, a sight support can be provided with a vertically oriented arcuate gauge at a convenient location near the rear of the sight. A lever which is pivotably connected to the support controls the elevation of a sighting element. Normally, the rear end of the lever is configured to travel in a path along the gauge which can accordingly be marked with, for example, an adhesive tape having distance indicia according to experimentally determined lever positions.
In practice, however, the distance settings made on an adjustable sight are only accurate for the particular arrow weight, tip weight and bow weight used to calibrate the sight. Individual shooting characteristics also affect the calibration settings. As a result, once a sight has been distance calibrated, frequent removal and resetting of the indicia on a sight's gauge to fine tune the distance calibration or recalibrate the sight according to various other operating variables is still required.
The Pro Tape adjustable yardage marker for the bow sight of my U.S. Pat. No. 4,541,179 (sold by Sight Master, Inc. of Townsend, Mont.) addresses this problem successfully. This device generally comprises a piece of aluminum which is fastened to the arcuate end of the sight by screws and having tape distance markings thereon. The screws can be loosened to linearly adjust the marker, eliminating any need to remove the tape or alter the distance indicia.
U.S. Pat. No. 5,465,491 also discloses an adjustable yardage plate having markings which are removable with a solvent.
There remains, however, a need for an improved bow sight having an adjustment mechanism for even quicker and more precise fine tuning and recalibration. The bow sight should also be precise, sturdy and simple to use.